astc: Create a LUT at compile time for encoding values

This commit is contained in:
ReinUsesLisp 2020-03-13 23:40:02 -03:00
parent e183820956
commit 801fd04f75
1 changed files with 19 additions and 7 deletions

View File

@ -161,6 +161,8 @@ private:
enum class IntegerEncoding { JustBits, Qus32, Trit };
struct IntegerEncodedValue {
constexpr IntegerEncodedValue() = default;
constexpr IntegerEncodedValue(IntegerEncoding encoding_, u32 num_bits_)
: encoding{encoding_}, num_bits{num_bits_} {}
@ -179,8 +181,8 @@ struct IntegerEncodedValue {
return totalBits;
}
IntegerEncoding encoding;
u32 num_bits;
IntegerEncoding encoding{};
u32 num_bits = 0;
u32 bit_value = 0;
union {
u32 qus32_value = 0;
@ -296,7 +298,7 @@ static void DecodeQus32Block(InputBitStream& bits, std::vector<IntegerEncodedVal
// Returns a new instance of this struct that corresponds to the
// can take no more than maxval values
static IntegerEncodedValue CreateEncoding(u32 maxVal) {
static constexpr IntegerEncodedValue CreateEncoding(u32 maxVal) {
while (maxVal > 0) {
u32 check = maxVal + 1;
@ -322,13 +324,23 @@ static IntegerEncodedValue CreateEncoding(u32 maxVal) {
return IntegerEncodedValue(IntegerEncoding::JustBits, 0);
}
static constexpr std::array<IntegerEncodedValue, 256> MakeEncodedValues() {
std::array<IntegerEncodedValue, 256> encodings{};
for (std::size_t i = 0; i < encodings.size(); ++i) {
encodings[i] = CreateEncoding(static_cast<u32>(i));
}
return encodings;
}
static constexpr std::array EncodingsValues = MakeEncodedValues();
// Fills result with the values that are encoded in the given
// bitstream. We must know beforehand what the maximum possible
// value is, and how many values we're decoding.
static void DecodeIntegerSequence(std::vector<IntegerEncodedValue>& result, InputBitStream& bits,
u32 maxRange, u32 nValues) {
// Determine encoding parameters
IntegerEncodedValue val = CreateEncoding(maxRange);
IntegerEncodedValue val = EncodingsValues[maxRange];
// Start decoding
u32 nValsDecoded = 0;
@ -371,7 +383,7 @@ struct TexelWeightParams {
nIdxs *= 2;
}
return CreateEncoding(m_MaxWeight).GetBitLength(nIdxs);
return EncodingsValues[m_MaxWeight].GetBitLength(nIdxs);
}
u32 GetNumWeightValues() const {
@ -780,12 +792,12 @@ static void DecodeColorValues(u32* out, u8* data, const u32* modes, const u32 nP
// figure out the max value for each of them...
u32 range = 256;
while (--range > 0) {
IntegerEncodedValue val = CreateEncoding(range);
IntegerEncodedValue val = EncodingsValues[range];
u32 bitLength = val.GetBitLength(nValues);
if (bitLength <= nBitsForColorData) {
// Find the smallest possible range that matches the given encoding
while (--range > 0) {
IntegerEncodedValue newval = CreateEncoding(range);
IntegerEncodedValue newval = EncodingsValues[range];
if (!newval.MatchesEncoding(val)) {
break;
}